Crankcase breather pipe set-up

Bottom End (crankcases and crankshaft)
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55PAN
Posts: 50
Joined: Fri Jul 13, 2007 8:03 am
Bikes: 1982 FLHC
Location: NE Illinois

Crankcase breather pipe set-up

#1

Post by 55PAN »

I noticed in another thread that it was mentioned not to seal the breather tube. Well here's what my bike has. About ten years ago the previous owner put on a belt drive primary system and removed the pipe and sealed the breather hole and turned off the primary oiler. Then he drilled a hole in the oil tank dipstick and installed a nipple, put a hose on it and ran it towards the ground. When I got the bike it had been sitting for a year and there was a LOT of oil in the crankcase from sumping. When I kicked it you could here it sloshing around and when it started it all went back into the oil tank, none on the ground, it was about two quarts worth. I have since put over five hundred miles on it with no problems and it is pretty oil tight, no major leaks to speak of.
So I guess my question is... Is the motor breathing through the vent line to the oil tank and then through the hose on top of the dipstick? It's apparently been like this for ten years so it can't be that bad, could it? By the way the bike is a '55 FL.
Bruce

Hey guys, I know my post above was a little long but I still would like to know what you think of this set-up. In other posts people like "DuoDave" and "Plain" have said not to seal the breather tube but my set-up is a little different and I would like to know what you think about it. Thanks in advance for your opinions.



PanPal
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Re: Crankcase breather pipe set-up

#2

Post by PanPal »

I don't have an answer for you. I know how it is to write a thread and not get a reply. It sounds interesting and may work. It worked for 10 years. If I were running a belt, I'd look more into this, but I personally would probably route the pipe to the rear chain instead.

Plain
Posts: 80
Joined: Mon Nov 22, 2004 11:18 pm

Re: Crankcase breather pipe set-up

#3

Post by Plain »

48Pan:

I think that the reason that you are not getting a lot of opinions is that this is a real butt scratcher. I have given it some thought and I do not have a "good" answer. I would not have done this. The breather huffs out a LOT of air. My opinion is that there is no really good gas relief on my oil tank, and the possibility exists that the tank and engine would pressurize. But, you are operating successfully with the set up, and it has been like that for a long time. The tip off would seem to be that the engine is not leaking oil in odd places, which it almost certainly would be if pressure was building up. You may well have taught this old dog a new trick. I don't run a belt on the primary because a chain gives me many more options for changing gears to get the ride I like. That and the fact that even in the face of advancing technology I remain a contrary old coot and think that a motorcycle should have a chain!
I remain skeptical that your engine is breathing correctly with this setup, but that certainly does not mean that it is not. It is taking me a while to get my head around this. It is a butt scratcher.

Adios-----Plain BSM

55PAN
Posts: 50
Joined: Fri Jul 13, 2007 8:03 am
Bikes: 1982 FLHC
Location: NE Illinois

Re: Crankcase breather pipe set-up

#4

Post by 55PAN »

PanPal and Plain; thanks for the reply. If the bike came with a chain primary I probably would have left it that way. This '55 is a birth year bike and I've been riding for over 33 years and I guess I kind of go for the old way of doing things, but I have to admit so far I really like this belt drive. For the time being I'll probably leave the venting this way since it doesn't seem to be causing a problem, but I would still like to hear anyboby elses opinion on this.

DuoDave
Posts: 235
Joined: Tue Mar 16, 2004 10:45 pm

Re: Crankcase breather pipe set-up

#5

Post by DuoDave »

Many bikes have the engine breather venting into the oil tank. As you suggest, I suspect that when your breather opens, the crankcase pressure is escaping up the oil tank vent line into the oil tank. Since it seems to have worked okay so far, you may as well stick with it. Bet you have got the other guys running belt drives thinking now!

Toymaster
Posts: 29
Joined: Mon May 01, 2006 11:59 am

Re: Crankcase breather pipe set-up

#6

Post by Toymaster »

How big [ID] is the nipple and hose that 'vents' to the atmosphere?
I would think that the 'vent line' would be marginal to double as a breather, but it does seem to be working OK..
I would say that that 'vent' should at LEAST equal the 'vent line' in size..
And yes, an idea might be to aim that hose at the rear chain.. I would think there would be a 'mist' that would lube the chain [ but it COULD contain moisture also.. food for thought tho!]

55PAN
Posts: 50
Joined: Fri Jul 13, 2007 8:03 am
Bikes: 1982 FLHC
Location: NE Illinois

Re: Crankcase breather pipe set-up

#7

Post by 55PAN »

I checked the ID of the nipple and line that vents off the top of the dipstick and it is 1/4", which is about the same size as the nipple on the outside of the oil tank that the vent line from the motor is connected to. Also I think you have something there about a mist coming out of the hose. The hose is aimed at the frame brace that the seat post goes through and it always has an oil film on it. Maybe I will figure out a way to re-direct it to the rear chain.

By the way in case anybody is wondering, I changed my "name" to 55PAN from 48PAN since I sold the '48 and now have this '55FL.......Bruce

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